Although he admitted stabbing the five-year-old Alsatian outside his £750,000 house in Cryfield Grange Road, Gibbet Hill, a district judge ruled his actions were lawful because he feared his 11-year-old pet Bertie was going to die.

Max died at the scene from a single stab wound to the heart. Bertie survived his injuries.

Speaking outside court after the verdict, Mr Deeley, who runs a successful city centre lettings agency, said: “It’s the right result.

“I can honestly say I had explored every other practical avenue but I was left with no other alternative but to protect my family pet.

“It’s been an awful event from the time Max came through the hedge and attacked Bertie. The whole thing was just awful. Max was very aggressive.

“He was bought as a guard dog from the police while next door was being renovated. The one thing I could not believe was the size of him: he was twice the size of Bertie, and very fast. I felt so vulnerable.

“Stabbing him in the leg might have meant he could have turned on me so I just went for the biggest part of his body.

“I didn’t mean to kill him; if I had wanted to kill him I would have gone for the throat.”

Mr Deeley, who celebrated his 50th birthday yesterday, said Bertie was a gentle dog who had been in the family since he was a puppy.

“He was bought as a companion for my mum who had terminal cancer,” he said.

“He plays with all my nephews and nieces. He is loved by everybody.”

Max belonged to next door neighbour Tarlo Singh and lived untethered in a kennel at the front of the 34-year-old’s imposing mansion.

Mr Singh had claimed in court that Mr Deeley was lying in wait with the knife and had lured Max to his death.

The two men had previously fallen out in a dispute over boundaries. But speaking after the trial Mr Deeley said: “There was still some civility between us and I didn’t have any problems with Max.

“It’s just totally wrong to say I was lying in wait for him.”

Mr Deeley added he was “surprised” the case got to court and said he just wanted life to “return to normal”.

Returning a not guilty verdict moments earlier, deputy district judge David Miller said: “On November 26, Max, a five-year-old Alsatian, went into the grounds of Mr Deeley’s house and attacked Bertie, an 11-year-old Labrador.

“Bertie was no match for Max. Max was dominant and Bertie submissive. Max was a particularly large dog; Bertie a lively, but somewhat ageing, Labrador.

“Max pinned Bertie down by locking its jaws onto Bertie’s throat. This attack was serious and could have been fatal.

“Mr Deeley, a dog lover, felt an immediate need to protect Bertie, and was in fear of his own safety.

“He was faced with a scene in which Max’s jaw was locked onto Bertie’s throat and a serious injury was caused close to critical parts: windpipe and arteries.

“He genuinely believed in the circumstances that the action he took was the only solution. I am not sure Mr Deeley believed he acted disproportionately.

“This is a tragic case and I have every sympathy for Max who may not have had murderous intentions towards Bertie.” The judge added: “This verdict is no way meant to condone the use of a weapon on a dog, but these were exceptional circumstances.”